I'd make it so you could tap a phone, you know their phone number, you know their email. Importantly in my eyes, you shouldn't be able to navigate to a profile and just ask to connect as that'd mean you could do that to people you don't actually know (whereby knowing is inferred by you knowing some amount of their personal info such as tap, phone, email).

I'd stay away from your last option of 'other platforms', per my other reply below in that those platforms allow you to connect to anyone/anything. There is nothing in them that say this connection is inherently personal vs being generic.